This invention relates generally to an immersion control device and associated alarm that establishes a fluid pressure within a fluid filled cushion or mattress and detects a fluid pressure change within the fluid filled cushion, and more particularly, to a device for establishing a fluid pressure and then detecting a fluid pressure change within a fluid filled cushion or mattress used to support an object or an individual in a bed, a wheelchair or other seat or support. This invention provides means to regulate the fluid pressure in the fluid filled cushion or mattress in response to the detected fluid pressure change and, if desired, sound a suitable alarm in response to an over or under pressure condition.
The device of the present invention provides means for establishing the proper or desired depth in which to immerse an individual into a fluid filled device (such as air filled or water filled cushion or mattress), for example a wheelchair cushion or a mattress without "bottoming out". Proper immersion into the cushion, mattress or support device as it may be referred to hereinafter, increases the amount of the surface area of the skin of an individual or support area of an object that is contacted by the fluid filled cushion or mattress or support device. The greater the amount of surface area that can be used to support an object or an individual the greater the reduction in a peak and average pressures on the object or on the skin of the individual. In the case of an individual having decubitus ulcers or pressure sores, reduction of these peak and average pressures exerted on the skin is of primary importance. In the case of fragile or volatile objects reduction of these peak and average pressures exerted on the object can be important to protect against breakage or other damage in the event of a bump or shock to the object. It is desired to minimize the peak and average pressures.
The device of the present invention is particularly useful for handicapped individuals confined to wheelchairs or beds. The present invention is generally applicable as part of a seat support system in automobiles, trucks, airplanes, or other supports in which one remains seated for extended time periods. It will be understood that while the device of the present invention has numerous applications the following description will be directed to preferred embodiments of the invention as intended for use by a handicapped, paralyzed or partially paralyzed individual.
The presently available devices attempt to immerse the individual as deeply as possible. However, a desired immersion without "bottoming out" can only be arrived at presently by trial and error.
Presently, the only way of determining that the proper depth of immersion into the fluid filled cushion or mattress has been achieved is to insert a finger, fingers or the entire hand under the position of the bony prominences of the body, such as the ischial tuberosities in the buttocks. This method is not easy for a handicapped individual to accomplish and often not possible at all because of physical impairments. Even this crude and inaccurate method is often not understood by care givers and is carried out differently by individual care givers generally resulting in many different immersion depths and with the resultant ranges of fluid pressures in the fluid filled cushion or mattress. These ranges of fluid pressures result in various performance ranges of peak and average contact pressures on the skin of the individual supported by the fluid filled cushion or mattress.
Another problem, particularly with respect to air filled cushions, is the leakage of minute amounts of air. Air leakage can cause the immersed individual to "bottom out" in the device and lose all of the benefits derived from the air filled support device. Paralyzed individuals are particularly susceptible since they could have no sensation in the buttocks and do not realize that they are resting not on the support device but on an underlying support surface and that they have "bottomed out".
In the conventional devices alarms have been provided to signal the departure of a patient from a hospital bed, U.S. Pat. No. Re. 28,754 for bed egress alarm circuit reissued Mar. 30, 1976 to Cook et al, Reissue of U.S. Pat. No. 3,852,736, issued Dec. 3, 1974; and an air inflated flexible bag has been provided to be placed below the mattress of a hospital or nursing home bed and connected to a pressure actuated electrical switch signal at a remote attendant's station, to signal removal of a patient's weight from the mattress, U.S. Pat. No. 4,020,482 issued Apr. 26, 1977 to Feldl for patient monitor. An inflatable pad is disclosed in U.S. Pat. No. 3,533,095 issued Oct. 6, 1970 to Collins for inflatable pad with alarm consisting of an inflatable pad to which is secured a pressure switch maintained in a line connected to a power source with an indicator and buzzer activated when the pressure switch plunger is advanced by the placement of a weight on the inflatable pad and closing a circuit to activate the buzzer and indicator light. Another mattress and alarm combination is shown in U.S. Pat. No. 3,631,438 issued Dec. 28, 1971 to Lewin for apnoea alarms comprising a compartmented air mattress with individual compartments connected to a common chamber containing an anemometer connected to an electric circuit which gives an alarm after a pre-set time if there is no airflow over a katharometer normally caused by the movement of the mattress as the result of a breathing baby lying on it.
In the conventional devices pressure sensitive switches have been provided. U.S. Pat. No. 4,172,216 issued on Oct. 23, 1979 to O'Shea for pressure sensitive switch discloses a resilient insulative layer of a plastic foam material sandwiched between a dimpled carbon powder loaded plastic foam pad in which the dimples extend through holes in the insulative layer and are intended to be placed under a bed mattress as a mattress-switch indicating electrically by means of contact between the plastic sheet and the foam pad the presence of an occupant in the bed or his absence by lack of such contact. U.S. Pat. No. 3,860,773 issued Jan. 14, 1975 to Fontaine for composite seat and switch with recessed contacting sheet discloses a base panel, a resilient pad, a pair of contacting sheets and a seat cover integrated together with one of the contacting sheets in a recess in either the pad or the panel and there between so as to be separated from the other contacting sheet, wherein the contacting sheets close when a person sits on the seat cover and open when the person leaves as a result of the resilient action of the pad. U.S. Pat. No. 4,086,458 issued on Apr. 25, 1978 to Dickey for electrical switch for use by the disabled discloses a switch comprising a resilient contact assembly including a pair of electrical conducting members in a housing in which the conducting members are maintained out of electrical contact with each other by means associated with the assembly such that application of pressure to the housing closes the switch.
In the conventional devices, such as alarms and pressure sensitive switches, a signal is generated in response to a physical action such as getting in or out of a bed. The conventional devices do not provide for any corrective action in response to the signal. The conventional devices do not provide for the adjustable support of an individual confined to a bed or wheelchair.
The immersion control device and associated alarm of the present invention solves these and other problems in a manner not disclosed in the known prior art.